THE ADIPOSE LOBE OF THE PELVIC PIN OF THE SALMON. 705 
outer angle of the pelvic fin is a character which is common 
to a wide range of members of that class. This “accessory 
scale/’ if I may so term it, is particularly characteristic of 
the more primitive Teleosteans, and is almost invariably 
absent in highly specialised forms; it is often well developed 
in actively swimming forms, and absent, or much reduced, in 
forms which haunt the ground. Only in the genus Salmo, 
so far as I am aware, is the accessory scale converted into 
an adipose lobe, and only in this genus, and. perhaps in 
Coregonus, has it any skeletal connection with the fin- 
rays of the pelvic fin. 
The nature of the function which this adipose lobe serves 
is obscure, but it is possible that it may assist in facilitating 
the rapid movements for which this fish is noted. The 
subject will be treated more fully at the conclusion of this 
paper. 
I wish to acknowledge my indebtedness to Miss P. C. 
Esdaile, M.Sc., for permission to remove the portions of the 
salmon (which had been supplied by J. A. Hutton, Esq., for 
work upon which she was engaged) which I required, also 
for furnishing me with various particulars as to the size, age, 
locality and condition of the several specimens. To Professor 
Lorrain Smith I am indebted for the use of apparatus in the 
Pathological Department, and for his ready assistance in 
determining the nature of the fat in the adipose fins. 
Finally, I am glad of this opportunity gratefully to acknow- 
ledge the kindness of Professor J. W. Spengel for granting 
me a table for work in his laboratory at Giessen, and for the 
use of apparatus and materials; also that of Professor J. 
Versluys for his friendly interest and for many illuminative 
suggestions. 
Figs. 1 and 2 illustrating this woi'k were prepared from 
photographs kindly undertaken respectively by Mr. J. T. 
Wadsworth, of the Zoological Department at Manchester 
University, and by Mr. A. W. Brown, of the Gatty Marine 
Laboratory at St. Andrews. 
